Phase lock-in thermography for metal walls characterization

Phase lock-in thermography is a nondestructive and contactless technique used for characterization of materials. We present in this paper a new method to characterize the thermal diffusivity of a material by knowing, at different frequencies, the phase shift between a modulated laser power and the thermal signal of a plate sample by the laser heating. This method is based on a three dimensional analytical model of thermal Fourier amplitude. By using a numerical modeling, a new formula was found out to calculate the thermal diffusivity. We also present a developed experimental setup. It was applied to verify this method with Inox 304L, Nickel samples and it gives results with 5% accuracy. This method shows an interest for characterization of hardly accessible components which require a contactless measurement. (authors)